1. Field of the Invention
The invention relates to polyamides and more particularly relates to water thinnable polyamide compositions useful as components of aqueous printing ink compositions.
2. Brief Description of the Prior Art
Polyamide resins which are useful in aqueous ink compositions have been described in the prior art literature; see for example the descriptions given in the U.S. Pat. Nos. 3,355,409; 3,776,865; 3,778,394; 3,844,991; 3,882,090; 3,945,983; and 4,365,041. In spite of the wide variety of polyamide containing, aqueous ink compositions known through the prior art descriptions, there has remained a need for improved polyamide resin components and ink compositions.
We have developed a new water reducible (thinnable) polyamide resin composition for use in aqueous flexographic inks. Such inks are useful for aqueous flexographic printing of polyethylene and polypropylene packaging films. The major advantage of the polyamide of the invention is that it will allow preparation of inks containing water as a significant replacement for the organic solvent (alcohols, hydrocarbons etc). presently required to dissolve conventional polyamides used in non-aqueous flexographic printing. Such waterborne ink will assist printers in complying with solvent emission standards (1970 Clean Air Act) as well as reducing solvent costs. In addition water is readily available, is non-toxic, and non-flammable.
Such waterborne inks will also retain the gloss, color strength, flexibility, adhesion and anti-blocking properties common to non-aqueous polyamide inks on preferred substrates such as polyethylene and polypropylene.